#include <cstdint>
#include <iostream>
#include <istream>
using ll = int64_t;

ll n,one,two;

int main(){
    std::iostream::sync_with_stdio(false);
    std::cin.tie(nullptr);

    std::cin>>n;
    for(ll i=1;i<=n;i++)one+=i&1,two+=!(i&1);
    std::cout<<one*two<<"\n";
}